Heat Sealing Jaw, Apparatus and Method

ABSTRACT

This invention relates to a heat sealing element for use in a heat sealing jaw in cooperation with an opposing backing jaw for sealing layers of film together to form a sealed portion and a notch within the sealed portion, the heat sealing element comprising: a sealing face for pressing the layers of film together against the opposing backing jaw and forming the sealed portion, the sealing face having a protrusion for forming the notch within the sealed portion; and a clamping portion adjacent to the sealing face, the clamping portion being disposed at an orientation diverging from a plane along which the layers of film are sealed together.

CROSS-REFERENCE TO RELATED APPLICATION

This application is filed under the provisions of 35 U.S.C. §121 andclaims priority to U.S. patent application Ser. No. 12/220,606, filed onJul. 25, 2008, which in turn claims priority to the U.S. ProvisionalPatent Application No. 60/962,517, filed on Jul. 30, 2007. Bothapplications are incorporated herein in their entirety.

FIELD OF THE INVENTION

This invention relates generally to the production of packaging pouchesand more specifically to a heat sealing jaw that is suitable forproducing an easy-open feature on a packaging pouch.

BACKGROUND

Packaging pouches are typically made on form, fill and seal machines.For example, using a vertical form, fill and seal machine, a flat web ofsynthetic thermoplastic film is unwound from a roll and formed into acontinuous tube in a tube forming operation, by sealing the longitudinaledges of the film together to form a lap seal or a fin seal. The tubethus formed is pulled vertically downwards to a filling station. Thetube is then collapsed across a transverse cross-section of the tube,the position of the cross-section being at a sealing device below thefilling station. A transverse heat seal is made by the sealing device atthe collapsed portion of the tube, thus making an airtight seal acrossthe tube. The sealing device generally comprises a pair of jaws.

After making the transverse seal, but before the jaws of the sealingdevice are opened, a quantity of material to be packaged, for example aliquid, is caused to enter the tube at the filling station, and to fillthe tube upwardly from the aforementioned transverse seal. The tube isthen caused to move downwardly a predetermined distance. This movementmay be under the influence of the weight of the material in the tube, orit may be caused by pulling or mechanically driving the tube The jaws ofthe sealing device are closed again, thus collapsing the tube at asecond transverse section. The second transverse section may be above,usually just above the air/material interface in the tube, or the secondtransverse section may be below the air/material interface. The sealingdevice seals and severs the tube transversely at the second transversesection. The material filled portion of the tube is now in the form of apillow shaped pouch. Thus the sealing device has sealed the top of thefilled pouch and sealed the bottom of the next pouch to be formed, allin one operation. The filling of the product may be conducted on acontinuous or intermittent basis. One such vertical form, fill and sealmachine of the type described above is sold under the trade-mark PREPAC.Other suitable machines are sold under the trade-marks INPACO andELECSTER.

A variety of flowable materials may be packaged in this manner, forexample, milk, syrups, sauces, juices, water and the like. The term“flowable material” can include materials that are flowable undergravity or may be pumped. Such materials may include emulsions, pastes,peanut butter, preserves, dough, ground meat, powders, detergents, oilsand granular solids. Such pouches can also be used to contain otherflowable materials such as foods that are packaged under sterile,pasteurized or aseptic conditions. The packaging conditions willnormally require modifications to the machine and also modifications tothe methods of packaging.

The pouches produced through this type of process can be manufactured tocontain any volume of flowable material. In the situation where drinkingfluids are packaged in this fashion, a typical size might be 250 mls or500 mls. In such instance, it is possible to consume the fluid directlyfrom the pouch. Thus, providing a pouch that includes an easy-openfeature for this purpose is desirable especially when served incorrectional facilities since it avoids the necessity to use animplement such as a knife or scissors. In addition, since these packagesare meant for one-time use and are disposable, it is appropriate thatthe manner in which they are manufactured is as economical as possible,without sacrificing the basic packaging requirements for the materialsin question.

Many solutions have been proposed for producing packages of this type,and typically such packages have included a notch or tear line whichallows the package to be opened. For example, French Patent No. 1 216422 discloses liquid-filled polymer pouches that are produced bycollapsing a tube and having an easy-open feature. The easy-open featurecomprises a sealed area partially extending across the width of thepouch and a weakened line extending within the sealed area. The weakenedline is formed using a set of jaws where one jaw comprises a piano wire.

United Kingdom Patent No. 898,641 discloses a pouch having a line ofweakness for easy opening that is produced by pressing the sheet betweena solid plate and a ribbed die while heat is applied. The sheet ispinched between the plate and the rib of the die and reduced inthickness but not sheared, or otherwise punctured along the desiredline.

U.S. Pat. No. 5,038,550 and European Patent No. 0 372 886 both disclosepouches having a slit formed within a sealed portion. The slit isintended as a device for starting a tear and for directing the tear in apreferred direction. In both cases the sealed portion is formed firstusing a sealing element and then the slit is formed using a separatecutting operation using a knife.

U.S. Patent Application Publication No. US 2006/0110081 A1 published onMay 25, 2006, discloses a pouch for containing a flowable material,provided with an easy-open feature located adjacent to an upper closureor a lower closure of the pouch. The easy-open feature comprises a sealformed between two layers of film and provides a tear line for openingthe pouch and tearing a corner off the pouch.

One concern with easy-open features in packaging pouches is that duringthe production, filling, handling or any manipulation of the pouches,stresses are induced in the film that forms the walls of the pouch.Therefore, depending on the configuration of the easy-open feature, itmay produce a stress concentration in the film and hence make the filmmore susceptible to tearing in specific areas.

Thus there is a need for an improved heat sealing jaw that can be usedto easily and economically produce an easy-open feature in a pouch thatis sufficiently robust to withstand stresses induced on the pouch duringmanipulation and/or filling of the pouch.

SUMMARY OF THE INVENTION

Accordingly, the present invention provides a heat sealing jaw which canbe used to produce a packaging pouch with an easy-open feature, whereinthe easy-open feature does not significantly compromise the integrity ofthe packaging pouch.

According to one aspect, the present invention provides a heat sealingjaw for use in cooperation with an opposing backing jaw for sealinglayers of film together to form a sealed portion and a notch within thesealed portion. The heat sealing jaw comprises a jaw body, a heatsealing element secured to the jaw body, a support surface associatedwith the heat sealing element for clamping the layers of film againstthe opposing backing jaw and a heat sink coupled to the heat sealingelement. The heat sealing element has a sealing face for pressing thelayers of film together against the opposing backing jaw and forming thesealed portion. The sealing face has a protrusion for forming the notchwithin the sealed portion. The heat sink is coupled to the heat sealingelement at a location adjacent to the support surface, and duringoperation, the heat sink induces a temperature gradient along thesealing face of the heat sealing element.

Advantageously, the heat sealing element may further comprise a clampingportion that is disposed at an orientation diverging from a plane alongwhich the layers of film are sealed together. This tends to facilitatethe securing of the heat sealing element to the jaw body which may alsoserve as the heat sink.

According to another aspect, the present invention also provides a heatsealing jaw for use in cooperation with an opposing backing jaw forforming an easy open feature adjacent to an edge of a packaging pouchmade from layers of film sealed together. The heat sealing jaw comprisesa jaw body, a heat sealing element secured to the jaw body, a supportsurface associated with the heat sealing element and a heat sink coupledto the heat sealing element. The heat sealing element has a sealing facefor forming a sealed portion extending inwardly from the edge of thepouch. Accordingly, the sealing face has an outboard end to bepositioned outside of the edge of the pouch, an inboard end to bepositioned inside the edge of the pouch and a protrusion for forming thenotch within the sealed portion. The support surface is associated withthe inboard end of the sealing face for clamping the layers of filmagainst the opposing backing jaw. The heat sink is coupled to the heatsealing element at a location adjacent to the inboard end of the sealingface, and during operation, the heat sink induces a temperature gradientalong the sealing face of the heat sealing element.

According to another aspect, the present invention provides a heatsealing element for use in a heat sealing jaw in cooperation with anopposing backing jaw for sealing layers of film together to form asealed portion and a notch within the sealed portion. The heat sealingelement comprises a sealing face for pressing the layers of filmtogether against the opposing backing jaw and forming the sealedportion, and, a clamping portion adjacent to the sealing face. Thesealing face has a protrusion for forming the notch within the sealedportion. The clamping portion is disposed at an orientation divergingfrom a plane along which the layers of film are sealed together.

According to a further aspect, the present invention provides a methodof sealing layers of film together to form a sealed portion and a notchwithin the sealed portion comprising the steps of:

-   -   a) providing layers of film to be sealed together between a heat        sealing jaw and a cooperating backing jaw, the heat sealing jaw        comprising a heat sealing element with a sealing face having a        length and a protrusion extending partly along the length of the        sealing face;    -   b) inducing a temperature gradient along the length of the        sealing face of the heat sealing element, wherein a first        temperature of the sealing face adjacent to the protrusion is        higher than a second temperature of the sealing face at a        distance from the protrusion;    -   c) closing the jaws to press the layers of film between the        sealing face of the heat sealing element and the backing jaw,        and, to simultaneously clamp the film at a location adjacent to        the sealing face;    -   d) holding the jaws closed for a period of time required to form        the sealed portion and the notch; and    -   e) opening the jaws to release the layers of film.

The above method may be performed on a pouch forming and filling machinesuch as a vertical form, fill and seal packaging machine, in conjunctionwith additional steps that are required to form a packaging pouch havingan easy-open feature and filled with flowable material. Accordingly, thelayers of film may be provided between the heat sealing jaw and thecooperating backing jaw in the form of a film tube that is partiallyfilled with flowable material. The temperature gradient along the lengthof the sealing face may be induced by extracting heat from the heatsealing element using, for example, a heat sink coupled to the heatsealing element.

BRIEF DESCRIPTION OF THE DRAWINGS

Further details of these and other aspects of the present invention willbe apparent from the detailed description and figures included below,which are exemplary and included for illustrative purposes. Thoseskilled in the relevant art(s) will understand that the followingdescription and drawings and are not intended to limit the scope of theteachings herein in any way.

Reference is now made to the accompanying figures, in which likereferences are intended to refer to like or corresponding parts:

FIG. 1 is an isometric view of a heat sealing jaw according to anembodiment of the present invention;

FIG. 2 is an isometric view of the heat sealing jaw of FIG. 1 with aclamp removed;

FIG. 3 is an isometric view of a heat sealing element from the heatsealing jaw of FIG. 1;

FIG. 4 is a cross-sectional view of the heat sealing element of FIG. 3along line 4-4 in FIG. 3;

FIG. 5 is a front elevation view of a packaging pouch having aneasy-open feature formed using the heat sealing jaw of FIG. 1;

FIG. 6 is an isometric view of the heat sealing jaw of FIG. 1 positionedin relation to an opposing resilient backing member;

FIG. 7 is a front elevation view of the heat sealing jaw of FIG. 1positioned in relation to a film tube used for producing the pouch ofFIG. 5; and

FIG. 8 is an isometric view of the heat sealing jaw of FIG. 1 positionedwithin the filling compartment of a vertical form, fill and sealpackaging machine.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring now to FIG. 1, a heat sealing jaw, generally shown at 10, foruse in cooperation with an opposing backing jaw (not shown) for sealinglayers of film together is shown. The heat sealing jaw 10 can be used ona vertical form, fill and seal (VFFS) packaging machine for producing aneasy-open feature on a pouch containing flowable material.

Many types of films can be used to manufacture pouches in accordancewith the present invention. Generally these films must be capable ofself-sealing and processing through the VFFS equipment. They should bestiff enough and strong enough for the proposed packaging applications.The nature of the packaging application determines the film selectionand the person skilled in the art would be capable of readily selectinga suitable film for the desired purpose. Examples of suitable filmsinclude any synthetic thermoplastic polymeric film which meets theabove-mentioned criteria. The films may contain a barrier layer selectedfrom nylon polymers, polyethylene terephthalate polymers, amorphousnylon or ethylene vinyl alcohol. An additional tie layer may be presentand can be selected from ethylene vinyl acetate polymer, ethylene acidcopolymers, ionomers or anhydride functionalized ethylene copolymers.All of these may be combined with at least one high pressure ethylenehomopolymer. Other examples of suitable films are described in thefollowing references: WO 98/34844, WO 98/29249, WO 97/20693, WO97/12755, WO 95/21743, WO 95/10566, WO 95/00587, the disclosures ofwhich are incorporated herein by reference. These are merelyrepresentative examples of thermoplastic films and the invention is notto be limited in any way with respect to the film selected formanufacture of the pouch.

As shown in FIGS. 1-4, the heat sealing jaw 10 comprises a jaw body 12and a heat sealing element generally shown at 14 secured to the jaw body12. The heat sealing element 14 comprises a sealing face 16 having afirst end 18 and a second end 20, and, a back face 22. The heat sealingelement 14 also has a clamping portion 24 that is disposed at anorientation diverging from the sealing face 16, which is also divergingfrom a plane along which the layers of film are sealed together duringoperation. The sealing face 16 has a rib-shaped protrusion 26 which islocated at a distance from the second end 20.

The heat sealing element 14 is secured to the jaw body 12 by clampingthe clamping portion 24 of the heat sealing element 14 to the jaw body12 using a clamp 28. The clamping portion 24 of the heat sealing element14 is thermally and electrically connected to the jaw body 12 so thatthe jaw body 12 can also serve as an electrical terminal of the heatsealing element 14. The heat sealing element 14 is also electricallyconnected to terminal 30 which is electrically isolated from the jawbody 12.

A thermal insulator 32 is also disposed on at least a portion of theback face 22 of the heat sealing element 14 so as to thermally insulatethe heat sealing element 14 from the jaw body 12 in a region adjacent tothe sealing face 16.

Referring now to FIG. 5, an exemplary packaging pouch generally shown at34 and made in accordance with the present invention is shown. The pouch34 is made by sealing layers of film together and comprises an uppertransverse seal 36, a lower transverse seal 38 and a longitudinal finseal 40. The pouch 34 also has an easy-open feature 42, disposed alongor adjacent to a side edge 44 of the pouch 30. The easy-open feature 42can be made using the heat sealing jaw 10 and comprises a sealed portion46 and a notch 48 within the sealed portion 46.

In order to seal the layers of film together and produce the easy-openfeature 42 on the pouch 34, the heat sealing jaw 10 works in cooperationwith an opposing conventional backing jaw which is not shown. However, aresilient backing member 50 which is part of the opposing backing jaw isshown in FIG. 6. The structure and configuration of such backing jawsare known to one skilled in the art. The heat sealing element 14 isheated by resistance heating and the layers of film are pressed togetherbetween the heat sealing jaw 10 and the resilient backing member 50.

The protrusion 26 on the sealing face 16 forms the notch 48 within thesealed portion 46 of the easy-open feature 42. The geometry of theprotrusion 26 may be selected based on the notch geometry desired. Thenotch 48 may comprise an indentation, a cut or any type of materialweakness formed within the sealed portion 46 that can be used toinitiate tearing of the layers of film and thereby facilitate theopening of the pouch 34. For example, the protrusion 26 may be selectedto produce a notch which extends completely through the layers of filmthat are sealed together or to produce a notch which only partiallyextends through the layers of film so as to form a weakened region ofreduced thickness. Other shapes and configurations of protrusions toproduce any variety of notches may also be used. In differentembodiments, the weakened region may be made prior to or at the sametime as the perimeter seal.

As shown in FIG. 6, the resilient backing member 50 may extend beyondthe area of the sealing face 16 of the heat sealing element 14 so thatduring the sealing process, the film layers are simultaneously clampedbetween the resilient backing member 50 and a support surface 51associated with the heat sealing element 14. The support surface 51 maybe provided by at least a portion of at least one of the thermalinsulator 32, the jaw body 12, and the clamp 28. Depending on theprocess conditions, a portion of the sealing face 16 adjacent to thesecond end 20 may also provide some support for clamping the filmlayers. The support surface 51 serves to stabilize the film around thearea where the sealed portion 46 is being formed. Providing adequatesupport or film clamping adjacent to or at the second end 20 of thesealing face 16 during the sealing process can be beneficial inproducing a good quality seal.

The difference in elevation between the heat sealing element 14 and thesupport surface 51 produces a pressure profile across the resilientbacking member 50 during the sealing cycle and causes any flowablematerial in the pouch 34 to clear the location of the easy-open feature42. This ensures that the flowable material inside the pouch 34 does notcontaminate the sealed portion 46 of the easy-open feature 42.

FIG. 7 shows the position of the heat sealing jaw 10 in relation to afilm tube generally shown at 52, during the process of producing pouches34 filled with flowable material on a VFFS packaging machine. Thepouches 34 are typically sealed and separated along a cut line 54 usinganother separate transverse heat sealing and cutting element (not shown)in order to form the transverse seals 36 and 38 on _(t)he pouch 34. Theseparate transverse heat sealing and cutting element, may be secured toa separate jaw or to the same jaw as the heat sealing element 14.Therefore, the easy-open feature 42 may be formed at the same time or ata different time as when the pouches 34 are sealed and separated alongthe cut line 54.

Also seen in FIG. 7, in an embodiment second end 20 of heat sealingelement 14 is seen to be within the film path of film tube 52 movingthrough the apparatus to form pouch 34, while first end 18 of heatsealing element 14 is outside the film path. In this arrangement, theinboard terminal associated with heat sealing element 14 is within thefilm path, and thus extends a distance towards the interior of pouch 34,while the outboard terminal associated with heat sealing element 14 isoutside the film path.

FIG. 8 shows the heat sealing jaw 10 installed within the fillingcompartment of an exemplary VFFS packaging machine. The fillingcompartment comprises transverse sealing jaws 58, longitudinal sealingjaws (not shown), a fill tube 60 and driven feed rollers 62. During theprocess of forming and filling pouches 34 in the VFFS machine, thetransverse sealing jaws 58 form a first transverse seal (36 and 38)across the film tube 52 then the vertically extending film tube 52 isintermittently fed downwardly by the driven feed rollers 62 by adistance corresponding to a height of the pouch 34 while beingsimultaneously filled with flowable material via the fill tube 60. Whenthe film tube 52 stops, the heat sealing jaw 10 in cooperation with theopposing backing jaw, forms the easy-open feature 42 and the transversesealing jaws 58 form the transverse seal 36 and 38 across the film tube52. The transverse sealing jaw may also simultaneously cut the film tube52 in order to separate the pouches 34 or weaken the film tube 52 inorder to form a string of separable pouches 34. Alternatively, the filmtube 52 may be cut via a separate operation using conventional meanssuch as a knife or the like. The longitudinal sealing jaws form the finseal 40 of the pouch 34. In the present embodiment, the heat sealing jaw10 is located above or upstream of the transverse sealing jaws 58 andactuated by a separate actuator 64. Alternatively, the heat sealing jaw10 could be disposed below the transverse sealing jaws 58 and/or beassociated with the same actuator as the transverse sealing jaws 58.

FIG. 7 further shows that the first end 18 of the sealing face 16 ispositioned on the outside of the side edge 44 or outboard of the filmtube 52 and that the second end 20 of the sealing face 16 is positionedon the inside of the side edge 44 or inboard of the film tube 52.Accordingly, the sealing face 16 of the heat sealing element 14 extendsacross the side edge 44 of the film tube 52 so as to produce the sealedportion 46 and the notch 48 which extend inwardly from the side edge 44of the film tube 52.

The heat sealing jaw 10 may also be positioned so as to orient the notch48 in the sealed portion 46 at an oblique angle from the side edge 44 asshown in FIG. 7. This provides the advantage that the easy-open feature42 can be used to facilitate the opening of the pouch 34 by tearing offa corner of the pouch 34. Advantageously, this may also reduce thestress concentration factor created by the easy-open feature 42 in thepouch 34. During filling and handling of the pouches 34, tensilestresses are induced in the walls of the pouch 34 and the obliqueorientation of the notch 48 of the easy-open feature 42 may reduce thetendency of the easy-open feature 42 to initiate failure of the pouch 34during filling and handling.

The clamping portion 24 of the heat sealing element 14 is thermallycoupled to the jaw body 12 via the clamp 28. Hence, the jaw body 12 andpotentially also the clamp 28 can serve as a heat sink to draw heat awayfrom the heat sealing element 14. This results in a temperature gradientbeing induced along the sealing face 16 wherein the temperature ofsecond end 20 of the sealing face 16 is lower than the temperature ofthe first end 18 of the sealing face 16. The higher temperature near thefirst end 18 of the sealing face 16 allows the protrusion 26 to form anotch which may extend completely through the film layers while thelower temperature of the second end 20 of the sealing face 16 is suchthat a seal is not formed between the film layers and therefore allowsthe seal to be terminated at this location. Such a temperature gradientis beneficial in forming a suitable transition between the sealedportion 46 and an unsealed portion of the pouch 34, which does notsignificantly compromise the integrity of the pouch 34. Depending on theprocess conditions, any portion of the sealing face 16 where thetemperature is such that no seal is formed between the film layers, mayeffectively serve to clamp and stabilize the film layers against thebacking jaw in addition and similar to the support surface 51.

A suitable temperature gradient along the sealing face 16 of the heatsealing element 14 may be achieved in a number of different ways. Forexample, depending on the process conditions (i.e. film material,configuration of easy-open feature, cycle time), it may be necessary touse a jaw body 12 that is actively cooled using liquid cooling or thelike. It may also be necessary to thermally isolate at least a portionof the heat sealing element 14 from the jaw body 12 using the thermalinsulator 32. A suitable material for the thermal insulator 32 could befor example a reinforced fibre glass material. Other choices would beapparent to those skilled in the art. The clamp 28 may also be thermallycoupled to the clamping portion 24 and contribute to the heat sink.Proper design and material selection and configuration of the jaw body12, clamp 28 and thermal insulator 32 for producing a suitabletemperature gradient along the sealing face 16 of the heat sealingelement 14 will depend on the process conditions and will be apparent toone skilled in the art. Accordingly, it is also apparent that thecomponents which contribute to the heat sink do not necessarily have tobe electrically coupled to the heat sealing element 14.

Depending on the process conditions, it may also be desirable to use arelease medium 56 between the heat sealing element 14 and the layers offilm so as to prevent the film from adhering to the heat sealing element14 when releasing the film following the sealing operation. The releasemedium 56 disposed on the sealing face 16 of the heat sealing element 14is illustrated in FIG. 4. Teflon® tape or film is suitable for thispurpose. Similarly, a release medium may also be disposed on theresilient backing member 50.

Depending on the process conditions, it may also be desirable to use anelectrical insulating medium between the back face 22 of the heatsealing element 14 so as to electrically insulate the heat sealingelement 14 from the jaw body 12. In one embodiment, the thermalinsulator 32 may also be an electrical insulator. In another embodiment,the electrical insulating medium can be Teflon® tape or a film suitableto provide electrical insulation. The tape or film may also extendbeyond the end of the thermal insulator 32 to provide electricalinsulation as far as the clamping portion 24. In some embodiments, theelectrical insulating medium may further provide additional thermalinsulation.

The above description is meant to be exemplary only, and one skilled inthe art will recognize that changes may be made to the embodimentsdescribed without department from the scope of the invention disclosed.It is apparent that the heat sealing jaw 10 described above can befabricated using conventional manufacturing procedures using suitablematerials that would be apparent to a person skilled in the relevantart. It is also apparent that other heat sink configurations may also beused for producing a suitable temperature gradient along the sealingface 16 of the heat sealing element 14. One skilled in the art wouldalso recognize that an easy-open feature located at a distance from afree edge of the pouch may also be produced using a heat sealing element14 wherein both the first section end 16 and the second section end 18are coupled to a heat sink and the sealing face does not extend acrossan edge of the pouch. It is further apparent that the heat sealing jaw10 is not limited to vertical form, fill and seal machines but couldalso be used on other types of packaging machines. Still othermodifications which fall within the scope of the present invention willbe apparent to those skilled in the art, in light of a review of thisdisclosure, and such modifications are intended to fall within theappended claims.

1-22. (canceled)
 23. A heat sealing element for use in a heat sealingjaw in cooperation with an opposing backing jaw for sealing layers offilm together to form a sealed portion and a notch within said sealedportion, said heat sealing element comprising: (a) a sealing face forpressing said layers of film together against said opposing backing jawand forming said sealed portion, said sealing face having a protrusionfor forming said notch within said sealed portion; and (b) a clampingportion adjacent to said sealing face, said clamping portion beingdisposed at an orientation diverging from a plane along which saidlayers of film are sealed together.
 24. The heat sealing element asdefined in claim 23, wherein said protrusion on said sealing face isdisposed at a distance from said clamping portion.